The murder charge against Abhisit Vejjajiva stems from the violent suppression of anti-government protests in 2010 when demonstrators were seeking to have Abhisit, Thaksin's rival, call early elections, saying he was in office illegitimately.

Thaksin was ousted as prime minister by a military coup in 2006 after being accused of corruption and disrespect to the monarchy. The protests and crackdown left more than 90 people dead and about 1,800 injured in Thailand's worst political violence in decades. Abhisit is accused by the Department of Special Investigation of allowing the unrestrained use of deadly force to quell the protest.

Speaking to reporters after meeting DSI officials, Abhisit said he had formally acknowledged the charge against him, but denied guilt. He said he would present documents supporting his position after studying the charge more closely. A court must still accept the case before it goes to trial.

The DSI specifically found reason to believe Abhisit culpable in the death of a taxi driver because he allowed troops to use war weapons and live ammunition against protesters. A recent criminal court inquest found security forces responsible for the man's death.

The shooting occurred during two months of demonstrations by Thaksin's supporters, known as the Red Shirts, who occupied a central intersection in the capital, Bangkok. As tensions grew, the army garrisoned the area around their encampment, while Abhisit lived at an army base for his own safety and security. Soldiers swept through barriers to forcefully end the protest on May 19, 2010.

Former deputy prime minister Suthep Thaugsuban, who was in charge of the special security agency set up to contain the protests, arrived with Abhisit to be charged with the same offence.

The political tide has shifted several times since Thaksin's removal. His sister Yingluck Shinawatra is prime minister, while Abhisit leads the opposition as head of the Democrat Party. Tharit was DSI chief during Abhisit's administration, and was widely seen then as his hatchet man for aggressively prosecuting Red Shirt leaders and supporters.

Thaksin is in self-imposed exile to avoid a two-year jail term for a conflict of interest conviction in 2008. Thaksin's supporters say he was unfairly convicted and would like to see him return without being jailed, while his opponents, such as Abhisit, insist that he not be let off the hook.

The case against Abhisit and Suthep is seen by many as a bargaining chip, to gain support for an amnesty that would cover many of the people charged or convicted of crimes in connection with the political battles after the coup. An amnesty to lift Thaksin's conviction would be would be more politically palatable if it covered Abhisit as well.